In a network, packets of data flow along paths in the form of traffic between endpoints. Routers located along the paths direct the data packets to other routers, until the data packets reach their destinations. Network links carry data packets directly between two routers, and each link is associated with a maximum flow capacity, or a maximum amount of data that the link can transfer within a unit of time. When traffic on a link is congested, meaning traffic is near or exceeds the flow capacity of the link, delays and possible loss of data packets occur. Thus, it is desirable to have a mechanism that provides reliable data indicating the amount of traffic on a link which can be used to adjust the traffic flows as necessary.